SELECT tar.direction, tar.code, MIN(tar.prefix) as prefix,
FROM tariff as tar
GROUP BY tar.direction, tar.code
ORDER BY tar.direction ASC
SELECT COUNT(*) AS total, (LEFT(dst,(LENGTH(MIN(tar.prefix))))) as pref
FROM
(
SELECT dst FROM cdrs WHERE LEFT(dst,(LENGTH(MIN(tar.prefix))))= tar.prefix GROUP BY dst
) AS t